The present invention relates to a mounting disk adapted to be fitted to a dental articulator for orthodontia and prostheses. The mounting disk is fitted with maxilla and mandible die models to reproduce the relationship of articulation between the upper and lower teeth. More particularly, the invention relates to a mounting disk for a mandible die model.
A conventional articulator, e.g., as described in Japanese Patent Laid-Open Publication No. 2000-42004 comprises, as seen in FIGS. 1-3, a pair of posts 2 vertically extending from a base 1, and a rotary plate 3 having one end pivoted to the upper ends of the pair of posts 2 by way of a pair of coordination mechanisms 50. The bottom surface of the rotary plate 3 is provided with a maxilla die mounting disk 5 for providing a maxilla die model 9 thereon. The top surface of the base 1 is provided with a mandible die mounting disk 6 for mounting a mandible die model thereon.
The vertical space between the maxilla die mounting disk 5 and the mandible die mounting disk 6 can be regulated by slide mechanisms 20 provided on the right and left posts 2. The mandible die mounting disk 6 is fitted to the base 1 in such a manner as to allow a displacement in the front-to-rear direction and a displacement in the rotational direction.
More specifically, as seen in FIGS. 13, 14 and 15, the mandible die mounting disk 6 is arranged rotatably relative to the base 1. A vertical rotary shaft 15 is threaded into a threaded hole 13 centrally formed in the mandible die mounting disk 6, the vertical rotary shaft 15 being inserted through a through hole 19 formed in a slider 18 from the opposite side of the base 1. The angle of rotation of the mandible dismounting disk 6 relative to the base 1 can be read using an indicator 36 formed in a seat plate 42 and a scale 37 formed on the circumference of the mounting disk 6.
The setting of the angle of rotation enables that position to be fixed by deeply screwing a guide screw 16 threaded into a threaded hole 26 of the slider 18 into an arcuate guide groove 12 formed in the rear side of the mounting disk 6. Reference numeral 11 denotes a reference groove.
The slider 18 is loosely slidably received in an elongated guide through hole 14 formed in the base 1 so that the slider 18 can be moved in the front-to-rear direction by holding a knob 24 of an operation rod fitted to the slider 18. The movement of the slider 18 allows the mandible die mounting disk to be positionally displaced and regulated in the front-to-rear direction. The distance of displacement can be read by use of a scale 39 formed on the side surface of the base 1 and an indicator 38.formed on the circumference of the mounting disk 6. By setting the distance of displacement, fixation at that position is achieved by means of a fixing screw 25.
The positional offset between the maxilla and mandible die models on the dental articulator can readily be judged by observing the positional offset between the right and left medial cut teeth, i.e., medial points of the maxilla and mandible die models. If the upper and lower medial cut teeth are positionally offset in the right-to-left direction, then the mandible die mounting disk 6 may rotationally be displaced up to a position in which the upper and lower medial cut teeth coincide with each other.
That is, if the upper and lower medial points Q1 and Q2 are positionally offset in the right-to-left direction as seen in FIG. 11a, then the mounting disk 6 may be turned in the direction of R1 around a center p1 of the mandible die mounting disk 6 up to a position in which the upper and lower medial points come into registration.
However, some patients may suffer a positional offset between the upper and lower molars despite registration of the medial points Q1 and Q2 as seen in FIG. 12a. n such an event, attempts to register the molar by rotating in the R1 direction around a mounting disk center p1 may cause a positional offset between the upper and lower medial points Q1 and Q2, as shown in FIG. 12b. 
It is therefore the object of the present invention to overcome the drawbacks of conventional articulators and to provide a mounting disk for a dental articulator having a coordination function to modify the patient""s jaw joint position reproduced on the articulator to a proper position in any case.
To achieve the above object, in the present invention, the mandible die mounting disk is vertically segmented into two parts so as to provide a function wherein the mandible die mounting disk is turned around its center axis relative to the articulator base, as well as a function whereby the mandible die mounting disk is turned around the extremity of the mandible die mounting disk, i.e., around the median point thereof.
According to one aspect of the present invention, there is provided a mounting disk comprising a lower rotary plate having at its substantially central portion a mounting portion for a vertical rotary shaft for mounting to a base of an articulator, and an upper rotary plate superposed on top of the lower rotary plate. The upper rotary plate has on its top surface a mandible model fixing portion for mounting a mandible model thereon. The lower rotary plate and the upper rotary plate are rotatably coupled to each other by way of a pivot member disposed at one end of each of the lower and upper rotary plates.
The mounting disk of the present invention may further comprise indication means which indicates a relative position between the lower rotary plate and the upper rotary plate, and locking means arranged to lock a relative position between the lower rotary plate and the upper rotary plate.
Preferably, the indication means includes an indication scale and an indicator. The indication scale indicates a relative position between the lower rotary plate and the upper rotary plate. Both the lower rotary plate and the upper rotary plate have an arcuate surface on their respective side faces opposite the pivot member. The arcuate surface has a center axis coincident with a pivotal axis of the pivot member. The indication scale is provided on the arcuate surface of one of either the lower rotary plate or the upper rotary plate. The indicator is provided on the arcuate surface of the other of the lower rotary plate and the upper rotary plate.
Preferably, the locking means includes an arcuate skirt, a horizontally extending slit formed in the skirt, and a locking rod passing through the slit. The arcuate skirt is formed by extending the arcuate surface of the other of the lower rotary plate and the upper rotary plate so as to cover the indication scale provided on the arcuate surface of the one of the lower rotary plate and the upper rotary plate. The locking rod has an extremity screwed into a threaded hole formed in the arcuate surface having the indication scale. The locking rod has at its midpoint an enlarged portion to fixedly tighten the skirt.